As required by Apple's privacy policies, users with Apple devices have the option to permanently delete their account.  

BEWARE!  Account deletion is PERMANENT  and IRREVERSIBLE and there will be no way to recover the account, progress, or any purchased assets from the game.; nor can any assets be transferred to a new account.  Once the account is gone, it's gone!  Crowdstar cannot restore deleted accounts. For this reason we strongly recommend securing your device against unauthorized use.

Get to the Settings screen by tapping the Settings icon in the upper left.

Tap the "Game Settings" screen.

Tap the "Delete Account"  button
Confirm deletion by tapping the check box, and tap the "Confirm" button.